Utility of Prospective Step Sections followed by Reverse Embedding Technique in Increasing Diagnostic Accuracy of Skin Biopsies

Abstract

Introduction: Small skin biopsies offer a cosmetic advantage to the patient but may provide limited information for making a diagnosis. Non specific and overlapping microscopic features often seen on superficial histopathology sections contribute to this challenge. In such cases, the use of step deeper and reverse embedding (re-embedding) sections has utility in improving diagnostic accuracy in dermatopathology practice. Aim: To examine the use of prospective step sectioning and reverse embedding in skin biopsies to improve diagnosis. Materials and Methods: This prospective, cross-sectional study included 200 consecutive skin biopsies received in the Department of Pathology, BGS Global Institute of Medical Sciences, Bengaluru, Karnataka, India, over an eight-month period from June 2022 to January 2023. Only skin biopsies smaller than 5 mm were included, while large punch biopsies (larger than 5 mm) were excluded. For each sample, a superficial section, step deeper section, and reverse embed section were taken. The pathologist reviewed the microscopic findings and rendered a diagnosis on the first slide. The other two slides were then reviewed, and the information provided by slides 2 and 3 was categorised as either no new information, additional information to make a diagnosis, or a change in diagnosis. Any change in diagnosis based on the information from slides 2 and 3 was noted and analysed. Results: Out of the 200 skin biopsies studied, 32 cases (16%) were non diagnostic on the first slide. Step deeper sections helped in making a diagnosis in 16 (8%) cases, and reverse embedding aided in the diagnosis of 9 (4.5%) cases. For the remaining seven cases where no additional information was obtained even after deeper and reverse embed sectioning, a descriptive report was provided. In eight (4%) cases out of the 200 biopsies where a diagnosis was made on the first slide, deeper/reverse embedding led to a change in diagnosis. Thus, deeper sectioning and reverse embedding improved diagnostic accuracy in 33 cases out of the total 200 skin biopsies studied (16.5%). Conclusion: This study highlights the utility of step deeper and reverse embed (re-embedded) sections in increasing diagnostic accuracy in small skin biopsies. Therefore, implementation of standardised protocol for studying multiple sections of small skin biopsies before rendering a diagnosis can significantly reduce diagnostic errors and aid in providing appropriate treatment to patients.